This invention relates to a bilirubin concentration measuring apparatus for transcutaneously measuring a bilirubin concentration in blood from the outside of a skin and a measurement data checking plate used therewith.
Generally, icterus, particularly severe icterus of new-born babies may cause a death or, even if they can escape from a death, it may progress to nuclear icterus which causes aftereffects such as cerebral palsy. Thus, the detection of icterus in an early stage is very crucial. The degree of icterus should be precisely detected by measuring a bilirubin concentration in blood serum collected from new-born babies. However, it is difficult to collect blood from all new-born babies and to measure the bilirubin concentration or it may bet often unnecessary.
Accordingly, the icterus of a patient has been diagnosed using an icterus detector disclosed in, e.g., U.S. Pat. No. 4,267,844 without collection of blood sample. This icterus detector includes a light source for emitting a light to the skin of a human body and at least two light receiving elements for responding to light components of the reflected light in at least two wavelength ranges whose absorption coefficients by bilirubin pigmented in subcutaneous fat differ from each other. The degree or stage of icterus is measured based on the outputs of the respective light receiving elements. In this way, the degree of icterus is indirectly measured by measuring the concentration of bilirubin pigmented in subcutaneous fat instead of measuring a serum bilirubin concentration.
However, since the above icterus detector measures the degree of icterus based on the reflected light from the skin, measurement results are likely to be influenced by a difference in the thicknesses of epidermis and derma located above the subcutaneous tissues containing fat where bilirubin is pigmented (e.g., a difference in the skin maturity of the new-born baby), the skin color of a patient, i.e., a race difference. Therefore, it is difficult to constantly and accurately measure the degree of icterus.